1. Field of the Invention
The present invention relates to communication networks, and, in particular, to nodes of a computer network that communicate using SATA and/or SAS protocols.
2. Description of the Related Art
IEEE 1394 (also referred to by the tradename FireWire) is a communication protocol standard for high-performance serial buses, that has gained popular use by providing mechanisms to interconnect home appliances, such as audio devices, video devices, scanners, printers, and computers. The IEEE 1394 standard is available from Institute of Electrical and Electronics Engineers, Inc., 3 Park Avenue, 17th Floor, New York, N.Y. 10016.
The original IEEE 1394 standard has evolved over the last decade into versions 1394a and 1394b, where IEEE 1394b requires that devices maintain backward compatibility to previous versions of the IEEE 1394 standard (e.g., IEEE 1394a). IEEE 1394 and 1394a devices operate at data rates of 100, 200, and 400 Mbps using data-strobe encoding, while IEEE 1394b devices operate at 400, 800, and 1600 Mbps with the clock embedded in the data. For backward compatibility, IEEE 1394b devices are also required to operate at 100, 200, and 400 Mbps using data-strobe encoding. Backward compatibility for IEEE 1394b devices requires relatively complex implementation, with increased number of gates and complex logic in the physical (PHY) layer portion of the standard.
FIG. 1 represents the data connections conforming to the IEEE 1394 standard for bidirectional communications between two device nodes (Nodes A and B) of a home network. As shown in FIG. 1, each node has an IEEE 1394-compliant port 102 having two interfaces (i.e., Twisted Pair A (TPA) and Twisted Pair B (TPB)), each interface supporting differential signaling over a different pair of wires (i.e., twisted-wire pair 104 and twisted-wire pair 106). In particular, data is transmitted via twisted pair 104 from the TPA interface of Node A to the TPB interface of Node B, while data is transmitted via twisted pair 106 from the TPA interface of Node B to the TPB interface of Node A, thereby providing two half-duplex connections for full, bidirectional communications between Nodes A and B. As indicated in FIG. 1, each node may have additional IEEE 1394-compliant ports, each having a TPA interface and a TPB interface.
Many home networks currently employ peripheral devices, such as hard-disk drives and/or other mass-storage devices such as magnetic/optical/flash memory, that use the Serial Advanced Technology Attachment (SATA) protocol and/or the Serial Attached SCSI (SAS) protocol as the communication protocol between the network's host processor and the peripheral devices. The operating data rates for SATA/SAS devices are at 1.5 Gbps and 3 Gbps. The SATA and SAS protocols are limited to host-to-peer communications.
Currently, some mass-storage products, such as hard-disk drives, employ a hybrid IEEE 1394 and parallel ATA protocol that requires a “bridge” chip to map IEEE 1394 protocol-based communications to ATA protocol-based data transfer and memory mapping at the hard-disk drives.